Description

Runs Apache Ant on a supplied buildfile. This can be used to build
subprojects. This task must not be used outside of a
target if it invokes the same build file it is part
of.

When the antfile attribute is omitted, the file "build.xml"
in the supplied directory (dir attribute) is used.

If no target attribute is supplied, the default target of the new project is
used.

By default, all of the properties of the current project will be
available in the new project. Alternatively, you can set the
inheritAll attribute to false and only
"user" properties (i.e., those passed on the command-line)
will be passed to the new project. In either case, the set of
properties passed to the new project will override the properties that
are set in the new project (See also the property task).

You can also set properties in the new project from the old project
by using nested property tags. These properties are always passed
to the new project and any project created in that project
regardless of the setting of inheritAll. This allows you to
parameterize your subprojects.

When more than one nested <property> element
would set a property of the same name, the one declared last will
win. This is for backwards compatibility reasons even so it is
different from the way <property> tasks in build
files behave.

Properties defined on the command line cannot be overridden by
nested <property> elements. Since Ant
1.8.0. the same is true for nested structures
of <ant> tasks: if a build file A
invokes B via an <ant> task setting a
property with a nested <property> element
and B contains an <ant> tasks
invoking C, C will see the value set
in A, even if B used a
nested <property> element as well.

References to data types can also be passed to the new project, but
by default they are not. If you set the inheritrefs attribute to
true, all references will be copied, but they will not override
references defined in the new project.

Nested <reference> elements
can also be used to copy references from the calling project to the
new project, optionally under a different id. References taken from
nested elements will override existing references that have been
defined outside of targets in the new project - but not those defined
inside of targets.

Parameters

Attribute

Description

Required

antfile

the buildfile to use. Defaults to
"build.xml". This file is expected to be a filename
relative to the dir attribute given.

No

dir

the directory to use as a basedir for the new Ant
project (unless useNativeBasedir is set to true).
Defaults to the current project's basedir, unless
inheritall has been set to false, in which case it doesn't
have a default value. This will override the basedir
setting of the called project.
Also serves as the directory to resolve the antfile and output
attribute's values (if any).

No

target

the target of the new Ant project that should be executed.
Defaults to the new project's default target.

No

output

Filename to write the ant output to. This is
relative to the value of the dir attribute if it has been set or
to the base directory of the current project otherwise.

No

inheritAll

If true, pass all properties to the
new Ant project. Defaults to true.

No

inheritRefs

If true, pass all references to the
new Ant project. Defaults to false.

No

useNativeBasedir

If set to true, the child build will use the same
basedir as it would have used when run from the command line
(i.e. the basedir one would expect when looking at the child
build's buildfile). Defaults to false. since
Ant 1.8.0

No

Parameters specified as nested elements

property

See the description of the property
task.
These properties become equivalent to properties you define on
the command line. These are special properties and they will always get passed
down, even through additional <*ant*> tasks with inheritall set to
false (see above).
Note that the refid attribute points to a
reference in the calling project, not in the new one.

Used to choose references that shall be copied into the new project,
optionally changing their id.

Attribute

Description

Required

refid

The id of the reference in the calling project.

Yes

torefid

The id of the reference in the new project.

No, defaults to the value of refid.

propertyset

You can specify a set of properties to be copied into the new
project with propertysets.

since Ant 1.6.

target

You can specify multiple targets using nested <target> elements
instead of using the target attribute. These will be executed as if
Ant had been invoked with a single target whose dependencies are the
targets so specified, in the order specified.

Attribute

Description

Required

name

The name of the called target.

Yes

since Ant 1.6.3.

Basedir of the new project

If you set useNativeBasedir to true, the basedir of
the new project will be whatever the basedir attribute of
the <project> element of the new project says (or
the new project's directory if the there is no basedir attribute) -
no matter what any other attribute of this task says and no matter
how deeply nested into levels of
<ant> invocations this task lives.

If you haven't set useNativeBasedir or set it to
false, the following rules apply:

The basedir value of the new project is affected by the two
attributes dir and inheritall as well as
the <ant> task's history. The current behaviour
is known to be confusing but cannot be changed without breaking
backwards compatibility in subtle ways.

If the <ant> task is in a "top level" build
file, i.e. the project containing the <ant> task
has not itself been invoked as part of a
different <ant> (or <antcall>)
task "higher up", the following table shows the details:

dir attribute

inheritAll attribute

new project's basedir

value provided

true

value of dir attribute

value provided

false

value of dir attribute

omitted

true

basedir of calling project (the one whose build
file contains the <ant> task).

omitted

false

basedir attribute of the <project> element
of the new project

If on the other hand the <ant> task is already
nested into another invocation, the parent invocation's settings
affect the outcome of the basedir value. The current task's dir
attribute will always win, but if the dir attribute has been omitted
an even more complex situation arises:

parent dir attribute

parent inheritAll attribute

current inheritAll attribute

new project's basedir

value provided

any

any

value of parent's dir attribute

omitted

true

true

basedir of parent project (the one whose build
file called the build file that contains
the current <ant> task).

omitted

true

false

basedir of parent project (the one whose build
file called the build file that contains
the current <ant> task).

omitted

false

true

basedir of calling project (the one whose build
file contains the current <ant> task).

omitted

false

false

basedir attribute of the <project> element
of the new project

If you add even deeper levels of nesting, things get even more
complicated and you need to apply the above table recursively.

If the basedir of the outer most build has been specified as a
property on the command line (i.e. -Dbasedir=some-value
or a -propertyfile argument) the value provided will
get an even higher priority. For any <ant> task
that doesn't specify a dir attribute, the new project's basedir will
be the value specified on the command line - no matter how deeply
nested into layers of build files the task may be.

The same happens if the basedir is specified as a
nested <property> of an <ant>
task. The basedir of build files started at deeper levels will be
set to the specified value of the property element unless the
corresponding Ant tasks set the dir attribute explicitly.